I'm going to speculate about a few things regarding Deltarune here. People are saying a lot of things about whether or not this or that is going to happen and I thought to weigh in now that there is a second chapter out, and a clearer pattern has been established. Be warned, I'm taking EVERYTHING into account into speculation/analysis like this, so its heavy spoilers for a lot of stuff.

Spoiler: Deltarune chp2 speculation
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The Heart: Hero or Villain?
First must address, are we the players who control the Heart-not Kris, this is an incredibly important distinction-the Hero or the Villain of this story? This is a more complicated question to answer than it seems. The default assumption is that we're the Hero but the only reason we have to think that is because Ralsei explains that we need to save the world by closing the Dark Fountains. Except....we only have his word for that. Neither the Chaos King or the Queen seem to know or care about what the Fountains actually do, only caring what it does for them. Why does this one little fluffy goat boy know this when these two rulers didn't? We don't know where he came from or why he is an exception to the very rules he states. And we're railroaded into doing his agenda, no matter how merciless or merciful we are. For all we know, he is lying to accomplish some other objective.

At the same time, Villain doesn't really work unless we're playing genocide- which is much harder to do than in Undertale. To get the chapter 2 genocide you really need to work to derail things. Unless you do things very specifically and violently, your saving Darkners and putting them in Castletown.

Now there is the thing about the Heart possessing Kris and controlling their actions. Except Kris can seemingly pull out the Heart at any time and take back control without us being able to do anything about it. Then for some reason, Kris puts us back in once they are done doing whatever it is they want to do, even if all the things they do are incredibly creepy and with a zombie like gait. So is Kris really being controlled, or the Heart just forced into them and they keep it around for some reason when they need to do something without it and they allow us to control their actions to a degree? Because there are things that we don't control about Kris even if the Heart is inside them. Things we don't tell them to say, that turn to look at the camera after a cut scene is over, little things like that.

Like we didn't choose to possess Kris, someone else did that. We wanted to be put in some custom body of our own making. If we're doing something villainous its because we're a pawn of someone who has rigged the game in their favor- and Ralsei might be a pawn as well. Y'know, aside from the genocide route cruelty we can do for its own sake. But at the same time, the genocide run of Chapter 2 reveals that Ralsei may be aware that the Heart is controlling Kris, as well as that the Heart can control others to kill for you instead of Kris.

Kris: Troubled Teen or Villain?
Now we look at Kris. Are they simply a troubled teen who got unfairly possessed, or a villain actually orchestrating all this while we are not controlling them? I can see and make arguments for both and also the problems with those arguments. I will start with the troubled teen interpretation.

If Kris is nothing but a troubled teen who got unfairly possessed, then all they've done is eaten some cake during the night, slashed some tires and cause one Dark World to form because they agree with Susie about staying in one. Understandable, if unwise. The problem with saying Kris is a troubled teen or whatever... is that it makes no sense. They were raised in a good environment, with a good family and while there was a divorce its not as if Toriel or Asgore became any less loving or caring towards Kris. They still seem to be living a relatively good life. Even if Kris feels something about that, is it really enough to want to change the world and risk the apocalypse? Kris apparently was a troublemaker in their youth and did something at some point but its never elaborated on. Yet they are talked about as if they're this creepy silent child whose sudden interest in going around talking to people is out of character for them. Now you could say its just introversion, but even introverted people have some measure of talking to people. The way some people talk about Kris makes them seem like some husk or zombie that is just there for some reason. And I don't think normal teens no matter how troubled keep a birdcage around to tear out the soul inside their body and throw into whenever they need to. If Kris is nothing a but a troubled teen caught up in all this, we need a compelling reason for why they are this way. Also the way they walk and are presented is deliberately creepy and unsettling with no actual dialogue from them and the kind of plan to trap your own friend and family in a Dark World seems...a bit out there for an ordinary teen to do.

On the Villain interpretation side of things, it doesn't get any less murky. Chapter 2 ending implies that Kris is at least capable of causing the first two Dark Worlds at school and the library. In this interpretation, they ARE the Roaring Knight and for some reason are working to open the Dark Fountains for some purpose. Why the Roaring Knight wants the world to end- if that is indeed something that will actually happen- is a mystery. The problem with this is well...how does Kris know to do all this? In the chapter 2 ending it could plausibly be explained by them just doing it after hearing Ralsei or the Queens explanation of how Determination works to open this stuff up. If they were doing this since the beginning, they would somehow need to know beforehand to open up the other Dark Worlds before the third one. So where would they learn how to do it? Well for that we must ask: how did Ralsei learn all this in the first place? We know its very likely that Ralsei is a Darkner formed from Kris's own desires about Asriel and that Kris has studied the occult according to Catti. Ralsei might just be a pawn in Kris's plans, created to be this naive exposition figure to lie about Kris's real goals for why they close off other Dark Fountains and gather them all at Castle Town. However another problem with this possibility is if Kris is the Roaring Knight, how does the Chaos King and the Queen not recognize Kris when they come back a second time to close the fountain seemingly having switched sides? Now Kris could disguise themselves, Queen wasn't able to read Noelle's face and thus didn't recognize her at all because computer but that doesn't explain Chaos King not recognizing them.

The World: Saved or Doomed?
Another question to consider is whether the world of Deltarune is doomed or not. We only have two people knowledgeable and sane enough to tell us: Ralsei and Seam. Ralsei seems to think the world's destruction can be averted as long as you keep closing Dark Fountains. Seam seems to think that the end of the world is inevitable and has resigned himself to it. Now it could just be Seam being a pessimist. Would not be out of character for Toby Fox to use that old chestnut. But neither would I put it past Ralsei to be a liar or pawn who is somehow CAUSING the end of the world by empowering a single fountain.

There is however some evidence against the world being doomed: namely its only when you give up you get a dark start/title menu because you gave up after a death leading to a timeline where the world ended. If the world was doomed no matter what, why bother with any other background for the start screen? You may be on rails, but it seems as long as you don't give up those rails carry you to a timeline where the world does not end. Maybe.

But if the world was doomed anyways, it would explain a lot about Deltarune: your choices don't matter not because of any railroading, but because its all going to be destroyed at the end of the game, no matter how many you befriend or many levels you gain, the end of the world can't be averted and its all about the journey to get there. It would explain why there is only “one ending” despite the things you can do to change things to a degree. Either that or Toby Fox is operating on a very strange definition of “one ending”.

The other other possibility is that this is all leading to the world being saved no matter what we do, in which case the genocide run thing may be “sure you saved the world, but at what cost?”

How Far Off the Rails Can We Go?
Continuing from the last question, I will now ask: How far off the rails can we truly go before we get rerailed? Because if there is only one ending, but stuff like the Chapter 2 genocide route has things like Berdley dying/going unconscious and Noelle being turned into a icy magical weapon of doom that can one shot bosses, that implies there is an ending so strong that it can force it all back to one conclusion. Or that Berdley wasn't important to the plot at all and not required for how anything turns out, so we can do what we want to him. Whether Berdley lives or dies isn't important for the ending, so he doesn't matter in terms of plot. But this also means the mental state of Noelle isn't truly important for the end either- just that she lives. Which is interesting.

Like thats the only way I can find to square this circle of the game insisting you have no choice but can alter this or that. The changes you CAN make aren't actually vital to whatever will happen at the very end. So if the state of Berdley doesn't matter, it means that whatever the ending involves, killing Berdley doesn't change it. But somehow Queen knowing what Ralsei told her does because that happens no matter what. Spamton can either die on either route or just languish as a salesman among garbage if you decide to ignore him, so his story never mattered to the main plot. Similarly you can either ignore Jevil or fight him so whatever you do with him doesn't matter which is why you have options.

Another optional thing? How many darkners you recruit. So they don't really matter to the main plot. In short, the only things that mattered to Chapter 2 were: the Queen is informed of her plan not working and thus defecting and Noelle getting out of the dark world alive along with the main three. Just like the only things that mattered in Chapter 1 was Chaos King being defeated and the main three being victorious, it didn't HOW they were victorious so long as the condition was fulfilled.

So I think we can assume that for the next four chapters, the vital conditions will consist some form of defeating the final boss/leader of a Dark World and Kris, Ralsei and Susie getting out alive, with Noelle probably also living in each. Chapter 7 is when all bets are off. So in all probability there will be ways to go off script and no-mercy run it enough, but they will always result in the certain few conditions that actually matter for the next chapter to work. Chapter 7 is when anything can happen and be done because it will all lead to the same ending regardless.

So its less that your completely powerless, and more that anything can happen as long as certain required conditions are fulfilled at the end- you just don't know what those conditions are until you've played it. It also implies the five other kids are not important to the ending and can be killed in the five other chapters, if the pattern is followed, but the way the next Dark World was made implies this may not be how it unfolds, as unless one of the five remaining kids comes to check out why Kris's house is dark or whatever, the only people in this new Dark World are: Kris, Susie and Toriel.

Hero/Villain Pair Possibilities:
Heart Good, Kris Good:
In this possibility, both Kris and the Heart are good, just working at cross purposes because Kris understandably doesn't like being controlled and is a teenager with their own desires and feelings

Heart Good, Kris Bad:
In this possibility, Kris is the villain trying to do something bad and the Heart is placed in them by Gaster to stop them. It would Kris is probably the Roaring Knight somehow manipulating all these events to some end desirable to them.

Heart Bad, Kris Good:
If we're the villain of the story and Kris is good or neutral, then we're probably doing the bidding of Ralsei who is working towards some goal that involves the Dark Fountains but not the end of the world, or some entity that has made Ralsei THINK that the world is going to end, but is being manipulated into doing something else.

Heart Bad, Kris Bad:
In this, Ralsei and Kris both have some agenda beyond saving the world, but are working at cross purposes, this could be why there is only one end and Seam says the world is doomed: no matter who you side with it brings the Roaring anyways.

The Second Possessor:
Another possibility of course, is that Kris is controlled not only by us, but by a different entity when they tear out the Heart and there is actually three beings vying for control of the same body. Time will tell if this is true.

Ralsei: The Enigma?
A scene in the chapter 2 Genocide route implies that Ralsei knows when we imagine Susie doing something and thinks that kind of scene is supposed to happen and when. This adds further credence to the fact that Ralsei knows more than they are letting on, as it implies some level of future knowledge. Meaning him being ignorant or a pawn is less plausible as it implies that Ralsei knows enough about events to expect a certain cut scene to happen.

There is also the fact that Ralsei just....appeared in the Cyber World, showing up on his own. Without any help from Kris or Susie. How did he get there? Not exactly right next to his own Dark World like the first one. Also HOW did he know to get here? Again, the future knowledge seems to be happening with this one.

His claim of being a prince of darkness is as always, suspect. There is nothing backing this up and is only heightened by the fact that each Dark World's “monarchy” system is kind of arbitrary and fake? Queen and Chaos King just seem to take over because they're powerful not because they're actually meant to rule anything.

Also if we keep closing the Dark Fountains, we can't actually know if what Ralsei says about the Roaring is true or not, can we? Because each time its only two fountains opened for the first two chapters. For there to be danger of it actually happening, it has to be multiple fountains opening at once. So either we keep only closing one fountain at a time thus not being able to prove Ralsei's warnings...or the ante is going to get upped in later chapters. And things will get interesting if a lot of fountains are opened and the Roaring just doesn't happen now won't it? Because the question becomes: what actually happens then?

As well as “what happens when we succeed in Ralsei's plan?”